Classifications

• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
  • D01D5/00—Formation of filaments, threads, or the like
  • D01D5/0007—Electro-spinning
  • D01D5/0061—Electro-spinning characterised by the electro-spinning apparatus
  • D01D5/0092—Electro-spinning characterised by the electro-spinning apparatus characterised by the electrical field, e.g. combined with a magnetic fields, using biased or alternating fields

Definitions

• the present invention relates to a method for forming a fibre from a material, using an electric field, wherein said electric field is applied between at least two electrodes, and wherein a first electrode is formed by a capillary for supplying the material, which first electrode is brought to a first electrical potential.
• the invention further relates to a device for forming a fibre from a material, using an electric field, which device comprise a capillary for supplying a material, in which the capillary forms a first electrode for bringing the material to a first electrical potential, and which further comprises a second electrode.
• the invention further relates to an object formed by using a method or a device as described above.
• Such methods and devices are better known by the name of "electrospinning" in the industry.
• a material is introduced into a space by an electrode formed by a capillary, and is accelerated by means of a further electrode under the influence of an electric field.
• the electric field exerts a pulling force on the material, thereby stretching the material, so that a fibre is formed. Since the material has already been brought to a first potential upon exiting the capillary, the fibre will fan out after some time. After all, the charged fibre exerts an electrostatic force on itself.
• the second electrode is usually formed by an earthed plate, on which the fibre is deposited.
• the second electrode may for example be made up of a cylindrical body or reel capable of rotary motion, so that the fibre can be wound onto the reel.
• fibres typically ⁇ 10 m
• Such a method has this drawback that after the material has exited the capillary and is stretched into a fibre under the influence of the electric field, the fibre will fan out, as described above.
• One of the consequences of said fanning out of the fibre is that it is difficult to control the positioning of the fibre.
• the invention provides a method for forming a fibre from a material and directing said fibre, using an electric field, wherein the electric field is applied between at least two electrodes, and wherein a first electrode is formed by a capillary for supplying the material, which first electrode is brought to a first electrical potential, characterised in that a second electrode is brought to a second electrical potential for locally applying said second electrical potential in at least one point for the purpose of pulling the fibre in a specified direction, wherein the location of the point at which the second electrical potential is applied can be changed in a time-controlled manner.
• the invention is based on the perception that by concentrating a second electrical potential in one point, the field lines of the electric field, and thus the pulling force exerted on the fibre by the electric field, will likewise be directed towards this point.
• the location of this point can subsequently be changed dynamically, so that the electric field between the electrodes is changed dynamically and the fibre can be pulled in another direction.
• the fibre can thus be pulled in any desired direction by means of the electrode, so that it becomes possible to direct the fibre.
• the method can be used for realising geometrically complex structures constituted by fibres, for example for forming objects.
• the second electrode has a pointed end.
• the second electrode comprises a needle electrode and said at least one point is formed by an end of the needle electrode.
• a needle electrode can be easily moved within a space for changing the location of the point at which the second potential is applied in a time-controlled manner, so that it becomes possible to pull the fibre in a desired direction during manufacturing thereof.
• the second electrode consists of an arrangement or array of local electrodes, each local electrode being arranged for applying an electrical potential at one point.
• each local electrode forms a point in a system of coordinates
• the fibre can be directed to any desired local electrode, for example by (temporarily) bringing such an electrode of the array to the second potential.
• various local electrodes of the array are brought to the second potential for the purpose of pulling the fibre in various directions. This can take place in a time-controlled manner, for example.
• the method can be carried out very efficiently, since it is comparatively straightforward to bring the various local electrodes of the group to the second potential independently of each other, so that switching between the various electrodes can be performed quickly and efficiently. This makes it possible to effect last modifications in the fibre direction.
• a dielectric and optionally curved or suitably shaped substrate is disposed between the second and the first electrode for receiving the fibre.
• the second electrode may be disposed under the substrate, whilst the capillary that supplies the material is disposed above the substrate.
• the fibre By directing the fibre by means of the second electrode, the fibre can be deposited at any desired location on the substrate.
• a coating may, for example, be applied to the substrate by means of the fibre. It is also possible, of course, to use the substrate as a mould for a surface to be created by means of the fibre, for example if the substrate is selected such that no adhesive or binding forces between the fibre and the substrate takes place.
• the substrate therefore comprises a surface having a desired shape for forming a surface or fibre pattern corresponding to the shape of the substrate surface from the fibre that is to be received.
• the present method makes it possible to form complex structures from the fibre in a relatively simple manner, it may for example be used for forming so-called "scaffolds" or artificial objects for use in a human or animal body.
• Such scaffolds usually require complex surfaces and structures, as is the case with an artificial heart valve, for example. Said surfaces and structures can be produced in a relatively simple manner by using the method as described above.
• complex geometric structures and platforms in a precise manner may also be of importance in the electrotechnical and optical industries.
• complex structures having relatively small dimensions can be formed with great precision on printed circuit boards (PCBs) and the like, for example, in a relatively simple manner by using the method according to the invention.
• PCBs printed circuit boards
• a method wherein material is supplied by two or more capillaries, and wherein each of the first electrodes formed by the capillaries can be brought to a first potential for the purpose of pulling the fibres in a specified direction from each of said at least two capillaries.
• the force being exerted on the fibre by the electric field can be controlled by varying the strength of the electric field. If both the first and the second electrode are on the same potential, there will be no electric field between the electrodes and no force will be exerted on the fibre. If two or more capillaries are used for supplying material and the force being exerted on the material from the two capillaries can be controlled independently of the force being exerted on the material from the other capillaries, it will be relatively easy to realise complex structures by means of the method according to the invention.
• this can be achieved, for example, by interrupting the drawing of fibres from each of said at least two capillaries in a time-controlled manner, by bringing the first electrode formed by the capillary of the material of the fibre to be interrupted (temporarily) to the second potential.
• first electrodes or capillaries can be disposed a sufficiently large distance apart, so that the electrical force being exerted between first electrodes will not be large enough to interfere with the operating principle of the invention.
• a device for forming a fibre from a material, using an electric field, which device comprises a capillary for supplying a material, wherein the capillary forms a first electrode for bringing the material to a first electrical potential, and which furthermore comprises a second electrode, characterised in that the second electrode is arranged for locally applying a second electrical potential in at least one point for the purpose of pulling the fibre in a specified direction.
• the second electrode consists of an array of local electrodes, each electrode being arranged for locally applying a second electrical potential at one point.
• the device may furthermore comprise means for bringing each of the local electrodes of said array individually to the second potential. Said bringing of the local electrodes on the second potential may take place in a time-controlled manner, if desired.
• a fibre manufactured by using the device or a method as described above is provided.
• Figure 1A shows an embodiment of a device according to the invention
• Figure 1 B shows a further substrate, which can be used in a device according to the invention
• Figure 2 shows an electrode according to the invention, which consists of a group of local electrodes as well as means for addressing the same;
• Figure 3 shows a circuit diagram according to the invention for driving local electrodes of a group according to figure 2;
• FIG. 4 schematically shows another embodiment of the invention.
• FIG. 1 A is a schematic representation of a device according to the invention, which can be used for carrying out the method according to the invention.
• the device which is generally indicated at 1 , comprises a first electrode 3, which also forms a capillary for supplying a material 5 from which a fibre 8 can be formed.
• the device furthermore comprises a second electrode 7, which is positioned on the other side of a substrate or plate 10 relative to the first electrode 3.
• De electrode 7 is capable of movement in an X-direction, a Y-direction and/or a Z-direction under the substrate 10, as is indicated by the coordinate system 9.
• the electrodes 7 and 3 can be brought to a second potential by connecting them, for example, to a voltage source 14.
• said connection is schematically represented by cables 11 and 12.
• the capillary/electrode 3 is connected to a reservoir 16, from which the material 5 is supplied to the capillary 3 via a pipe 15.
• said pipe can be opened and closed by means of a valve 18.
• An electric field is created between the electrodes 3 and 7 by bringing said electrodes to the second potential. Since the electrode 3 is on a first electrical potential, the material 5 that exits the electrode 3 will be electrically charged as well. The material 5 that exits the capillary 3 will experience a pulling force under the influence of the electric field, which is mainly generated between the pointed ends of the electrodes 3 and 7. The material is stretched in such a manner that a fibre 8 is obtained. The exertion of the force on the material 5 will take place in the direction of the points of the electrode 7.
• the electrode 7 present at the underside of the substrate 10 By moving the electrode 7 present at the underside of the substrate 10 in the X-direction or the Y-direction, the fibre 8 being drawn may be moved in desired directions while being drawn, and thus it is possible to change the location at which the fibre 8 is deposited on the substrate 10. In this way a desired pattern of fibres can be obtained on the surface of the substrate 10. If a curved substrate is used instead of a flat substrate (such as the substrate 10 in figure 1A), or a substrate having a random three-dimensional surface, the electrode 7 can also be moved in the Z-direction for following the substrate surface. Said following can take place at the underside of the substrate, for example, as shown in figure 1a with regard to the substrate 10.
• the fibre pattern can be easily removed from the substrate 10 if no bonding between the fibre and the substrate has taken place, and be separately processed to obtain a product.
• the fibre can be separated from the substrate in a suitable manner, for example by using a suitable solvent.
• the substrate 10 may be provided with a coating or a surface on which no adhesive or binding force on the fibre takes place, or only to a limited extent, so that it can be easily removed from the substrate.
• the substrate 10 is schematically indicated as a flat plate.
• the substrate 10 may comprise a surface that has been given a desired shape, for example a saddle surface or a surface having a more complex shape, so that the substrate 10 can function as a "mould" for a three- dimensional surface to be formed of the fibre 8.
• An example of such a surface would be a cylindrical surface or a reel, which can function as a mould for forming a stent or a graft, for example.
• the electrode 7 can be moved on the inner side of the reel or the cylinder in that case, possibly in combination with a movement of the reel itself. It is also possible to use more complex surfaces, for example for manufacturing an artificial heart valve.
• the substrate 10 in figure 1A is the substrate the 13 that is shown in figure 1 B.
• the surface thereof comprises a deep and "steep" valley 17, whose walls are spaced relatively close together.
• the fibre can be deposited at any location on the substrate 13, and consequently also in the valley 17 and on the walls thereof.
• the second electrode 7 consists of a needle electrode, which can be moved in an X-direction or a Y-direction under the surface of the substrate 10, so that it is possible to "write" on the surface of the substrate 10 with the fibre 8, as it were.
• an alternative electrode 25 is shown, which could take the place of the electrode 7 in figure 1A, extending under the substrate 10.
• Said alternative electrode 25 consists of an arrangement or array of local electrodes, which may be formed as a flat plate, a flexible mass, a deformable surface or have any other desired shape.
• the array of local electrodes 25 comprises forty-nine local electrodes. It should be understood that the illustrated example is only a schematic representation and that it is possible to use a larger or a smaller number of electrodes, if desired.
• the local electrodes must have a small surface area so as to bring only one point on a surface to a second electrical potential, those skilled in the art will appreciate that 1 million electrodes, each having a surface area of about 0.1 x 0.1 mm 2 could readily be provided on a 10 x 10 cm plate, if desired.
• the array 25 is connected to a pair of addressing systems 27 and 28, which can designate a row or a column, respectively, of the array 25.
• the electrode 26 is for example activated by having the addressing block 28 designate the second column and having the addressing block 27 designate the fourth row.
• the local electrode is brought to a second potential upon activation thereof. Since the local electrodes of the group 25 can be activated independently of each other, a fibre to be drawn, such as the fibre 8 from the device 1 of figure 1A, can readily be pulled and moved in different directions. Those skilled in the art will appreciate that switching of such an embodiment can take place in a quick and efficient manner, thereby increasing the range of application of the invention.
• the addressing blocks 27 and 28 are controlled by a control unit 29, which can be programmed by a user by means of a computer 30, if desired.
• activating the local electrodes is to be understood to include, for example, the connecting of a local electrode to be activated to ground (for example the local electrode 26) if the capillary or first electrode, as well as the other local electrodes of the array 25, are for example on a first potential.
• Figure 3A schematically shows a possible addressing circuit for the array of electrodes that is shown in figure 2.
• the addressing blocks 37 and 38 address a plurality of conductors that form part of an array of conductors 36.
• a drivable switch 42 will be driven at the intersection 40 of the conductors if the conductors are interconnected in a manner that will be apparent to a person skilled in the art at the points of intersection 40 thereof, which switch can be switched to a conducting state, for example.
• the local electrode 48 is brought to a second electrical potential by switching the switch 42 to a conducting state, since the electrode 48 is connected to a controllable switch 42 via the connection 49.
• the positive side of the voltage source is connected to ground 45. It should be understood that a part of the group 47 comprising the local electrodes, such as the local electrode 48, has been broken away for the sake of clarity of the drawing. The broken-away part is schematically indicated at 35.
• Figure 3 shows a controllable switch 42, via which the voltage supplied by the voltage source 43 can be transferred to the electrode 48.
• the controllable switch may be substituted for a transistor, a thyristor, a triac, a diac or other electronic switching means.
• the addressing blocks 37 and 38 may be connected to a control unit, such as the control unit 29 that is shown in figure 2.
• FIG 4 shows another embodiment of the invention, in which two first electrodes 55 and 56 form the capillaries for supplying material for producing the fibres 63 and 64.
• the fibres produced by the device as illustrated are deposited on the substrate 59.
• the second electrode 60 Disposed under the substrate 59 is the second electrode 60, which is a needle electrode in the illustrated embodiment.
• Bringing either the electrode 55 or the electrode 56 to the same electrical potential as the electrode 60 achieves that no pulling force is exerted between the electrode 60 and the electrode (55 or 56) that have been brought to the same potential. It is important in that case that the two electrodes 55 and 56 be sufficiently screened from each other, in order to ensure that no pulling force will be exerted between the two electrodes 55 and 56.
• An electric field between the electrodes 55 and 56 must be sufficiently weak, therefore.
• Such screening can be implemented in various ways, with a simple screening being realised by spacing the electrodes 55 and 56 sufficiently far apart.
• the manner in which the two electrodes 55 and 56 can be screened or isolated from each other so as to suppress undesirable effects will be apparent to those skilled in the art .
• the advantage of the embodiment that is shown in figure 4 is that the fibres 63 and 64 can be arranged on top of each other and through each other on the substrate 59 in a desired manner.
• the fact is that the fibre 63 can be drawn independently of the fibre 64.
• the user has a choice between bringing the electrode 55 to the same potential as the electrode 60 and bringing the electrode 56 to the same potential as the second electrode 60.
• the fibres 63 and 64, respectively, can thus be drawn independently of each other.
• FIG 4 The embodiment that is shown in figure 4 is schematically represented, and only those parts are shown that are relevant to the invention. Those skilled in the art will appreciate that the device that is schematically shown in figure 4 will be provided with means for bringing each of the electrodes 55, 56 and 60 to an electrical potential. Instead of using the needle electrode 60, it is moreover possible to use a group of electrodes as shown in figure 2 or 3.
• the capillaries/electrodes 55 and 56 are connected to containers for supplying material for drawing the fibres 63 and 64.
• circuit diagram for switching the electrodes 48 of the group 47 that is shown in figure 3 is only a single circuit diagram used for switching a single electrode.
• the other electrodes of the group can be driven in a similar manner. All kinds of switching systems may be used for switching the electrodes.
• a plurality of switching elements, such as the controllable switch 42, may be integrated on an integrated circuit.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Textile Engineering (AREA)
• Nonwoven Fabrics (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 2005
  • 2005-04-22 NL NL1028847A patent/NL1028847C2/nl not_active IP Right Cessation
• 2006
  • 2006-04-18 EP EP06733007A patent/EP1871929A1/de not_active Withdrawn
  • 2006-04-18 WO PCT/NL2006/000200 patent/WO2006112697A1/en active Application Filing

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